343 lines
9.1 KiB
C
343 lines
9.1 KiB
C
/*
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* Aug 8, 2011 Bob Pearson with help from Joakim Tjernlund and George Spelvin
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* cleaned up code to current version of sparse and added the slicing-by-8
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* algorithm to the closely similar existing slicing-by-4 algorithm.
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*
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* Oct 15, 2000 Matt Domsch <Matt_Domsch@dell.com>
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* Nicer crc32 functions/docs submitted by linux@horizon.com. Thanks!
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* Code was from the public domain, copyright abandoned. Code was
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* subsequently included in the kernel, thus was re-licensed under the
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* GNU GPL v2.
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*
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* Oct 12, 2000 Matt Domsch <Matt_Domsch@dell.com>
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* Same crc32 function was used in 5 other places in the kernel.
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* I made one version, and deleted the others.
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* There are various incantations of crc32(). Some use a seed of 0 or ~0.
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* Some xor at the end with ~0. The generic crc32() function takes
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* seed as an argument, and doesn't xor at the end. Then individual
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* users can do whatever they need.
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* drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0.
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* fs/jffs2 uses seed 0, doesn't xor with ~0.
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* fs/partitions/efi.c uses seed ~0, xor's with ~0.
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*
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* This source code is licensed under the GNU General Public License,
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* Version 2. See the file COPYING for more details.
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*/
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/* see: Documentation/crc32.txt for a description of algorithms */
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#include <linux/crc32.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/sched.h>
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#include "crc32defs.h"
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#if CRC_LE_BITS > 8
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# define tole(x) ((__force u32) cpu_to_le32(x))
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#else
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# define tole(x) (x)
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#endif
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#if CRC_BE_BITS > 8
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# define tobe(x) ((__force u32) cpu_to_be32(x))
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#else
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# define tobe(x) (x)
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#endif
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#include "crc32table.h"
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MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>");
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MODULE_DESCRIPTION("Various CRC32 calculations");
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MODULE_LICENSE("GPL");
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#if CRC_LE_BITS > 8 || CRC_BE_BITS > 8
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/* implements slicing-by-4 or slicing-by-8 algorithm */
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static inline u32 __pure
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crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
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{
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# ifdef __LITTLE_ENDIAN
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# define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8)
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# define DO_CRC4 (t3[(q) & 255] ^ t2[(q >> 8) & 255] ^ \
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t1[(q >> 16) & 255] ^ t0[(q >> 24) & 255])
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# define DO_CRC8 (t7[(q) & 255] ^ t6[(q >> 8) & 255] ^ \
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t5[(q >> 16) & 255] ^ t4[(q >> 24) & 255])
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# else
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# define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8)
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# define DO_CRC4 (t0[(q) & 255] ^ t1[(q >> 8) & 255] ^ \
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t2[(q >> 16) & 255] ^ t3[(q >> 24) & 255])
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# define DO_CRC8 (t4[(q) & 255] ^ t5[(q >> 8) & 255] ^ \
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t6[(q >> 16) & 255] ^ t7[(q >> 24) & 255])
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# endif
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const u32 *b;
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size_t rem_len;
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# ifdef CONFIG_X86
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size_t i;
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# endif
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const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3];
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# if CRC_LE_BITS != 32
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const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7];
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# endif
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u32 q;
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/* Align it */
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if (unlikely((long)buf & 3 && len)) {
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do {
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DO_CRC(*buf++);
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} while ((--len) && ((long)buf)&3);
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}
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# if CRC_LE_BITS == 32
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rem_len = len & 3;
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len = len >> 2;
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# else
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rem_len = len & 7;
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len = len >> 3;
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# endif
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b = (const u32 *)buf;
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# ifdef CONFIG_X86
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--b;
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for (i = 0; i < len; i++) {
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# else
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for (--b; len; --len) {
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# endif
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q = crc ^ *++b; /* use pre increment for speed */
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# if CRC_LE_BITS == 32
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crc = DO_CRC4;
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# else
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crc = DO_CRC8;
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q = *++b;
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crc ^= DO_CRC4;
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# endif
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}
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len = rem_len;
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/* And the last few bytes */
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if (len) {
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u8 *p = (u8 *)(b + 1) - 1;
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# ifdef CONFIG_X86
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for (i = 0; i < len; i++)
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DO_CRC(*++p); /* use pre increment for speed */
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# else
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do {
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DO_CRC(*++p); /* use pre increment for speed */
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} while (--len);
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# endif
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}
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return crc;
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#undef DO_CRC
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#undef DO_CRC4
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#undef DO_CRC8
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}
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#endif
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/**
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* crc32_le_generic() - Calculate bitwise little-endian Ethernet AUTODIN II
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* CRC32/CRC32C
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* @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for other
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* uses, or the previous crc32/crc32c value if computing incrementally.
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* @p: pointer to buffer over which CRC32/CRC32C is run
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* @len: length of buffer @p
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* @tab: little-endian Ethernet table
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* @polynomial: CRC32/CRC32c LE polynomial
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*/
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static inline u32 __pure crc32_le_generic(u32 crc, unsigned char const *p,
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size_t len, const u32 (*tab)[256],
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u32 polynomial)
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{
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#if CRC_LE_BITS == 1
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int i;
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while (len--) {
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crc ^= *p++;
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for (i = 0; i < 8; i++)
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crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
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}
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# elif CRC_LE_BITS == 2
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while (len--) {
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crc ^= *p++;
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crc = (crc >> 2) ^ tab[0][crc & 3];
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crc = (crc >> 2) ^ tab[0][crc & 3];
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crc = (crc >> 2) ^ tab[0][crc & 3];
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crc = (crc >> 2) ^ tab[0][crc & 3];
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}
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# elif CRC_LE_BITS == 4
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while (len--) {
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crc ^= *p++;
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crc = (crc >> 4) ^ tab[0][crc & 15];
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crc = (crc >> 4) ^ tab[0][crc & 15];
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}
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# elif CRC_LE_BITS == 8
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/* aka Sarwate algorithm */
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while (len--) {
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crc ^= *p++;
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crc = (crc >> 8) ^ tab[0][crc & 255];
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}
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# else
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crc = (__force u32) __cpu_to_le32(crc);
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crc = crc32_body(crc, p, len, tab);
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crc = __le32_to_cpu((__force __le32)crc);
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#endif
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return crc;
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}
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#if CRC_LE_BITS == 1
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u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
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{
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return crc32_le_generic(crc, p, len, NULL, CRCPOLY_LE);
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}
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u32 __pure __crc32c_le(u32 crc, unsigned char const *p, size_t len)
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{
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return crc32_le_generic(crc, p, len, NULL, CRC32C_POLY_LE);
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}
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#else
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u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
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{
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return crc32_le_generic(crc, p, len,
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(const u32 (*)[256])crc32table_le, CRCPOLY_LE);
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}
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u32 __pure __crc32c_le(u32 crc, unsigned char const *p, size_t len)
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{
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return crc32_le_generic(crc, p, len,
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(const u32 (*)[256])crc32ctable_le, CRC32C_POLY_LE);
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}
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#endif
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EXPORT_SYMBOL(crc32_le);
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EXPORT_SYMBOL(__crc32c_le);
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/*
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* This multiplies the polynomials x and y modulo the given modulus.
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* This follows the "little-endian" CRC convention that the lsbit
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* represents the highest power of x, and the msbit represents x^0.
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*/
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static u32 __attribute_const__ gf2_multiply(u32 x, u32 y, u32 modulus)
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{
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u32 product = x & 1 ? y : 0;
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int i;
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for (i = 0; i < 31; i++) {
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product = (product >> 1) ^ (product & 1 ? modulus : 0);
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x >>= 1;
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product ^= x & 1 ? y : 0;
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}
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return product;
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}
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/**
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* crc32_generic_shift - Append @len 0 bytes to crc, in logarithmic time
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* @crc: The original little-endian CRC (i.e. lsbit is x^31 coefficient)
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* @len: The number of bytes. @crc is multiplied by x^(8*@len)
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* @polynomial: The modulus used to reduce the result to 32 bits.
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*
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* It's possible to parallelize CRC computations by computing a CRC
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* over separate ranges of a buffer, then summing them.
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* This shifts the given CRC by 8*len bits (i.e. produces the same effect
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* as appending len bytes of zero to the data), in time proportional
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* to log(len).
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*/
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static u32 __attribute_const__ crc32_generic_shift(u32 crc, size_t len,
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u32 polynomial)
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{
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u32 power = polynomial; /* CRC of x^32 */
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int i;
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/* Shift up to 32 bits in the simple linear way */
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for (i = 0; i < 8 * (int)(len & 3); i++)
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crc = (crc >> 1) ^ (crc & 1 ? polynomial : 0);
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len >>= 2;
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if (!len)
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return crc;
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for (;;) {
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/* "power" is x^(2^i), modulo the polynomial */
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if (len & 1)
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crc = gf2_multiply(crc, power, polynomial);
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len >>= 1;
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if (!len)
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break;
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/* Square power, advancing to x^(2^(i+1)) */
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power = gf2_multiply(power, power, polynomial);
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}
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return crc;
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}
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u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len)
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{
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return crc32_generic_shift(crc, len, CRCPOLY_LE);
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}
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u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len)
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{
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return crc32_generic_shift(crc, len, CRC32C_POLY_LE);
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}
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EXPORT_SYMBOL(crc32_le_shift);
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EXPORT_SYMBOL(__crc32c_le_shift);
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/**
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* crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32
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* @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for
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* other uses, or the previous crc32 value if computing incrementally.
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* @p: pointer to buffer over which CRC32 is run
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* @len: length of buffer @p
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* @tab: big-endian Ethernet table
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* @polynomial: CRC32 BE polynomial
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*/
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static inline u32 __pure crc32_be_generic(u32 crc, unsigned char const *p,
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size_t len, const u32 (*tab)[256],
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u32 polynomial)
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{
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#if CRC_BE_BITS == 1
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int i;
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while (len--) {
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crc ^= *p++ << 24;
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for (i = 0; i < 8; i++)
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crc =
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(crc << 1) ^ ((crc & 0x80000000) ? polynomial :
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0);
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}
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# elif CRC_BE_BITS == 2
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while (len--) {
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crc ^= *p++ << 24;
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crc = (crc << 2) ^ tab[0][crc >> 30];
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crc = (crc << 2) ^ tab[0][crc >> 30];
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crc = (crc << 2) ^ tab[0][crc >> 30];
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crc = (crc << 2) ^ tab[0][crc >> 30];
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}
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# elif CRC_BE_BITS == 4
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while (len--) {
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crc ^= *p++ << 24;
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crc = (crc << 4) ^ tab[0][crc >> 28];
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crc = (crc << 4) ^ tab[0][crc >> 28];
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}
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# elif CRC_BE_BITS == 8
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while (len--) {
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crc ^= *p++ << 24;
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crc = (crc << 8) ^ tab[0][crc >> 24];
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}
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# else
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crc = (__force u32) __cpu_to_be32(crc);
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crc = crc32_body(crc, p, len, tab);
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crc = __be32_to_cpu((__force __be32)crc);
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# endif
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return crc;
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}
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#if CRC_LE_BITS == 1
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u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
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{
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return crc32_be_generic(crc, p, len, NULL, CRCPOLY_BE);
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}
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#else
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u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
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{
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return crc32_be_generic(crc, p, len,
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(const u32 (*)[256])crc32table_be, CRCPOLY_BE);
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}
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#endif
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EXPORT_SYMBOL(crc32_be);
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